DX-394 Tips?
Nick Marsh
Bought a DX-394 today from rat shack. ANyone got any tips for improving
it?
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73
Nick Marsh
WB4SQI
Donald L. Tomkinson
First do a search for DX394 on the web.
The following is what I have gleaned. Some it has been modified for my
own use. Recommend you get the service manual if you intend to do any
mods.
1. AGC: Bridge C163 with 100uf cap for slow AGC, 47uf for fast AGC. C163
is located on the bottom of the main board with the radio knobs facing
you. It is on the right near center just below Q9 with four surface
mount components to the left.
2. Gain: Bridge a 4.7K ohm resistor across R184 (helps gain control).
3. BW: Bridge .01/.047/.22uf cap across R64 (narrower
bandwidth/crosstalk).
4. BW: Bridge .1/.22uf cap across R91 (narrower bandwidth/crosstalk).
5. Keyboard beep delete: Disconnect R156 on main board.
Subject: Noise Blanker
Here are 2 easy mods that will make the DX-394 noise blanker perform
better. The performance on AM is marginal and doesn't work at all on
CW/SSB. The mods will improve the AM blanker performance significantly
and allow it to work on CW/SSB.
1. Remove the bottom cover with the front of the receiver facing you.
Bridge a 150K resistor across R180. This resistor is the third component
toward the front from Q32 (don't count Q32). R180 should be black with
224 (220K) on it. This will re-bias Q33's base to a more sensitive
threshold.
2. Find Q34. It is to the right of Q32. Solder a Schottky diode (1N5817
or similar) from the collector of Q34 to a ground trace. The anode of
the diode should go to ground and the cathode (banded end) to the
collector of Q34. The collector is the single pin on the side of the
transistor facing the rear of the receiver. A 1N4148 or 1N914 will work
but not as well. This mod will now let the noise blanker work in the
CW/SSB mode. It allows capacitor C182 to reset (discharge) in between
noise pulses.
3. Replace the bottom cover and remove the top cover and find
potentiometer VR1 (close to the front of the unit). Set the pot about
midway and you are finished (Leave the pot alone @ first. Adjust later
after you have checked out the mods).
Don
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Location: N33d42m08s W117d59m24s Grid Square: DM13AQ UTC -8hrs.
Scanners: Air-8, AR2001, AR900, BC50, BC101, BC142 (mod Wx sats),
BC20/20, BC2500, FRG9600, HP100, HX1000, HX1500, Pro26,
Pro2004/5/6, Pro2045, Pro2046, Opto R10, R532, R7000,
Scout 40, SX200N.
Software: Deltacomm v3.9, Probe v3.0, ScanCat Gold v6.0,
ScanStar v3.66.
Shortwave: DC777, DX160, DX394, ICF2010, R70, R71A, R1000.
Donald L. Tomkinson
While doing the mods on my DX394B I found that the LSB/USB trimmers are
not in the schematic/PCB in the service manual. Are the trimmers part
of the difference between the A & B models? I would think that the
service manual would be published when the first production units ( A )
go down the assembly line.
My LSB X3 resonator was padded with 33pf & was 300Hz high. Ended up
using 47pf to bring it less than 50Hz off zero beat. USB ( 500Hz low )
was easily adjusted using the trimmer TC5 ( LSB trimmer TC4).
Don
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Location: N33d42m08s W117d59m24s Grid Square: DM13AQ UTC -7hrs.
jg...@pacificnet.net
In article <354C047F...@ix.netcom.com>#1/1,
"A"version nor the service manual!
Scott
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Fcathell
This must be the difference between the A and B versions. I have an A version
with no added fixed trim caps and no TC4 variable trimmer for LSB. This would
explain the notorious calibration problem on the earlier versions if the bfo
resonators were off.
Frank
James Aeschliman
In a previous article, dtm...@ix.netcom.com ("Donald L. Tomkinson") says:
>While doing the mods on my DX394B I found that the LSB/USB trimmers are
>not in the schematic/PCB in the service manual. Are the trimmers part
>of the difference between the A & B models? I would think that the
>service manual would be published when the first production units ( A )
>go down the assembly line.
>
There are three models of the DX-394, the original model, the Model A,
and the Model B. The service model appears to be for the original model
and has no information on either the Model A or the Model B.
--
Jim Aeschliman bb...@scn.org
Black Diamond, Washington KD7MK
SP
Yep, anything is better than the telescoping antenna that they provide. Just
touching the one on mine improves the signal at least 5 times. It's a nice
little receiver if you get the right antenna behind it...
SP
Nick Marsh wrote in message <354A63...@wwd.net>...
Donald L. Tomkinson
TC-4/TC-5 are not in my service manual either (or the schematic).
Take the top off the DX394. Look at the PCB nearest the front of the
radio. You should see 2 each blue cubes. These are the LSB/USB ceramic
resonators X2/X3. The one on the left side is LSB, the other USB. To the
outboard of each is a mini trimmer, TC-4/TC-5.
You will need (preferably non metallic) a small adjustment screwdriver.
If you have no trimmers you could add some or just add some capacitance
across the resonator to bring it closer to center freq.
Don
--
-
Location: N33d42m08s W117d59m24s Grid Square: DM13AQ UTC -7hrs.
Scanners: Air-8, AR2001, AR900, BC50, BC101, BC142 (for Wx sats),
Donald L. Tomkinson
You can get more signal in (not always a good thing!) compared to the
HI-Z by connecting to the telescoping antenna with an alligator clip.